powerpc: Drop orphaned VAS MAINTAINERS entry

The MAINTAINERS entry for VAS (Virtual Accelerator Switchboard) no
longer has any maintainers, it just points to linuxppc-dev, since commit
60496069 ("powerpc: Update MAINTAINERS for ibmvnic and VAS").

So just drop the VAS entry, all the paths are already covered by the
main powerpc entry, ie. the output of get_maintainer.pl is unchanged.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20230221101952.2697101-1-mpe@ellerman.id.au

MAINTAINERS

@@ -9789,13 +9789,6 @@ L:	netdev@vger.kernel.org
 S:	Supported
 F:	drivers/net/ethernet/ibm/ibmvnic.*
 
-IBM Power Virtual Accelerator Switchboard
-L:	linuxppc-dev@lists.ozlabs.org
-S:	Supported
-F:	arch/powerpc/include/asm/vas.h
-F:	arch/powerpc/platforms/powernv/copy-paste.h
-F:	arch/powerpc/platforms/powernv/vas*
-
 IBM Power Virtual Ethernet Device Driver
 M:	Nick Child <nnac123@linux.ibm.com>
 L:	netdev@vger.kernel.org